In December the conservation group, along with Greenpeace and the Natural Resources Defense Council, sued the U.S. government to protect the world's polar bears from extinction.

According to the conservationists, Earth's steadily rising temperature is causing the polar bear's habitat to melt. Many scientists say the warming is due, in part, to human activities such as driving cars and burning coal, which release heat-trapping gases into the atmosphere,

If the bears are given federal protection, they would be the first U.S. mammals officially deemed to be in danger of extinction because of global warming, the conservation groups said.

Rosa Meehan, the chief of marine-mammal protection at the U.S. Fish and Wildlife Service in Anchorage, Alaska, said the conservation groups presented sufficient information to merit a close look at the status of polar bears.

"It doesn't mean that we are going to list them or that we're not," she said. "We know things are changing. We know a lot more about polar bears than we did a few years ago. We need to review their status."

The Fish and Wildlife Service will spend the next 12 months examining scientific evidence about the changing Arctic environment and how it is affecting polar bears.

Life on the Ice

Polar bears live only in the Arctic, the northernmost region of Earth (see Arctic photos).

The bears, which can grow to about 8 feet (2.5 meters) long, depend on sea ice for their survival. They hunt their primary prey, the ringed seal, from the ice. They also travel, mate, and sometimes give birth on the ice.